PIP4681D

File in Section:
Service Bulletin
Bulletin No.:
Date:
PIP4681D
November, 2013
PRELIMINARY INFORMATION
Subject:
Random Bump Chuggle or Fishbite Sensation While Cruising At Approximately
1,300 RPM
Models:
2009-2013 Cadillac Escalade
2008-2013 Chevrolet Avalanche, Silverado, Suburban, Tahoe
2008-2013 GMC Sierra, Yukon, Yukon XL
2009-2010 Hummer H2
with 6.0L (RPO L76) or 6.2L (RPO L9H or L94) Engine
This PI was superseded to update model years. Please discard PIP4681C.
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern
Some customers may complain of a random bump, chuggle, or fishbite sensation when crowding the throttle slightly
with the TCC on while cruising at 35-60 MPH. Generally, this is most apparent at 1,100-1,400 RPM but the RPM may
vary slightly depending on body type, axle ratio, operating conditions, and road grade. In many cases, this may
occur when lugging the engine up an incline at these conditions with the TCC locked up. The hotter the ambient
temperature is the more pronounced this may be.
The Tech 2 may show a few random misfires at this time but no DTCs will be stored. This will occur with Active Fuel
Management active or inactive. This concern is normally more apparent if the TCC is commanded to full lock up with
a Tech 2, while the concern is normally improved greatly or eliminated if the TCC is commanded off. Temporarily
disconnecting the CMP actuator connector will normally improve the concern or change the RPM range that it occurs
at as well.
Recommendation/Instructions
If related SI diagnosis, bulletins, and PIs do not isolate the cause of this concern, compare this with an identically
equipped vehicle.
If another vehicle exhibits the same concern, this should be considered a characteristic of the vehicle and no repairs
should be performed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is
resolved without completing every step, the remaining steps do not need to be performed.